ASE A1 Engine RepairEngine Block AssemblyEasy
Which of the following conditions is MOST likely to cause excessive crankshaft end play?
- AExcessive piston-to-cylinder wall clearance.
- BA bent connecting rod.
- CWorn thrust bearing surfaces.
- DWorn main bearings (journal-to-bearing clearance).
Show answer & explanationAnswer & explanation
Correct answer: C. Worn thrust bearing surfaces.
Excessive crankshaft end play is caused by wear on the thrust bearing surfaces, which are designed to control the crankshaft's axial (front-to-back) movement. When these surfaces wear down, the clearance increases, leading to excessive end play.
Why the other options are wrong
- A. Excessive piston-to-cylinder wall clearance causes piston slap and oil consumption, not crankshaft end play.
- B. A bent connecting rod affects piston travel and rod bearing wear, not crankshaft end play.
- D. Worn main bearings cause excessive radial clearance, not axial end play.
Crankshaft End Play
The controlled axial (front-to-back) movement of the crankshaft within the engine block, regulated by the thrust bearing. It's essential for thermal expansion and preventing binding.
- Controlled by the thrust bearing (usually part of a main bearing).
- Too little end play can cause binding and thrust bearing failure.
- Too much end play can cause knocking, oil pressure loss, and wear on other components.
Memory trick: Thrust takes the push, or the crankshaft will mush.